It was understood by most that Harold was never to be told he was wrong -- not directly, anyway. Better to do it by subtly piling evidence in front of him until such point that he declares he always thought that way.
This method can be bypassed if you're under a year old. Lucy's features and general wailing certainly indicated something was wrong, even if Harold was convinced he'd changed her nappy only ten minutes ago.
Jasfoup and Julie were siding with Lucy and scent of fresh number twos.
Jasfoup sniffed. "Of course she hasn't Julie," he said. "I expect she's hungry."
Harold frowned. Better than always being right was the opportunity to prove Jasfoup wrong...
Image: The Art of Always Being Right